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Aluminum bushing to aluminum tube permanent joining (no welding/threading)

Mishaois1

Plastic
Joined
Aug 27, 2019
Hi,

I am looking for some information regarding productive joining methods of aluminum tube and shaft.
Thought about Crimping technology or shrink fit.
The purpose is to achive a permanent connection between aluminum tube and aluminum shaft.

Tube O.D- 20mm, tube I.D- 16mm

Shaft O.D- 16mm

The required axial load is about 1000N. There is no exposure to extreme temperatures.

It is intended to mass production process, so the assembly has to be quick and efficient.

I thought about producing a mold (built of 2 parts) and try to do it by crimping with hydraulic press. mold design will enforce preservation of the circular shape of the tube by the end of the crimping (photos attached).

If someone can share his knowledge about design "rule of thumbs" or links to some valuable information of crimping process (or other efficient option)- it would be very appreciated!

Welding, threading, gluing are not an option.

Thanks!
 

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A shrink fit is likely your best bet, but you'll want fixturing to ensure alignment and handling of the two parts, including forceful insertion if needed. Make sure this is reliable and fast, having the bushing stick part way in is irritating.

Check the hoop stress capacity of your tubing, then the CTE for the alloy to establish a reasonable interference fit. A freezer for the plug may be all that's needed, but warming the tube may be needed too depending on design interference. If the tubing is heat treated try not to let it get over 100C. There's no limit on cold temps.

I'd guess that around 0.04mm with close control on the diameters may be enough, but you should confirm with testing.
 
There are several machines that will crimp fittings on pipes. I’ve seen them where they roll the tube with a wheel on the outside, and I’ve seen scissoring type clamps. Seems like I’ve seen them for copper and black pipe.
 
The purpose is to achieve a permanent connection between aluminum tube and aluminum shaft.

Tube O.D- 20mm, tube I.D- 16mm

Shaft O.D- 16mm

I am looking for some information regarding productive joining methods of aluminum tube and shaft.
Thought about Crimping technology or shrink fit.
The purpose is to achieve a permanent connection between aluminum tube and aluminum shaft.

What levels of intentional or accidental torque are there? If there is much torque, an interrupted crimp of some kind may be needed.
 
The torque is neglectable here, the significant load that should be overcomed is the axial force.
 
Hollow shaft in pictures?

Your proposed die crimping could work but there is going to be some burr left and end result is not round. Crimp fit pipe connectors are pretty close to what you propose. Hydraulic hose crimper with segmented dies is not that far either..
 
Thanks for the answer.
Yes, the shaft is hollow. 8mm internal diameter.
We will deburr it if it would be necessary.
The final result should be as round as possible.
 
It's important to remember that many Al alloys do not have the ductility of other materials such as soft steels. If this is a hard alloy (like 6061-T6), then there's a chance that swaging, roll forming, etc. may induce fractures and leave the part weaker than ideal.

I still suggest a simple interference fit, although I would like it done with a chilling of the plug (and if needed a light heating of the tube) rather than a true press at room temp.
 
The main purpose that we want to achieve is fast assembly with reduced probability of human error as much as possible (like forgetting loctite.
 
It's important to remember that many Al alloys do not have the ductility of other materials such as soft steels. If this is a hard alloy (like 6061-T6), then there's a chance that swaging, roll forming, etc. may induce fractures and leave the part weaker than ideal.

I still suggest a simple interference fit, although I would like it done with a chilling of the plug (and if needed a light heating of the tube) rather than a true press at room temp.


We will test this possibility as well, thanks.
 
I think one applies the locktite to clean, freshly machined aluminum.

Or use industrial epoxy, as used to hold airplanes together. The key is that it is heat cure.

Talk to Boing about that, and all the pre-glueing prep needed.....
 








 
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